Posterior Segment and Neuro-Ophthalmic Disease
Posterior segment and neuro-ophthalmic items reward a systematic fundus and pupil examination and a disciplined approach to sudden vision loss.
Key posterior findings
Drusen and pigmentary change suggest AMD; metamorphopsia suggests choroidal neovascularization and warrants urgent OCT. Diabetic retinopathy staging depends on microaneurysms, dot-blot hemorrhages, IRMA, venous beading, and neovascularization at the disc or elsewhere. CRVO shows diffuse hemorrhages ("blood and thunder"); BRAO shows a pale retina with a cherry-red spot; Hollenhorst plaques indicate embolic carotid disease. Flashes, new floaters, and a curtain suggest a retinal tear or detachment - with pigment cells in the vitreous and a visible break, same-day referral.
Neuro-ophthalmic rules
An afferent pupillary defect indicates asymmetric optic nerve or extensive retinal disease. Papilledema is bilateral, preserves acuity until late, enlarges the blind spot, and demands imaging plus blood pressure. Optic neuritis causes pain on movement, reduced color vision, and a relative afferent defect; MS risk is stratified by MRI. Giant cell arteritis causes pallid disc swelling with altitudinal field loss, jaw claudication, and elevated ESR/CRP - treat with high-dose steroids immediately and biopsy within two weeks. Field patterns localize: bitemporal to the chiasm, homonymous to retrochiasmal disease.
Worked example
A 68-year-old reports sudden painless loss of the top half of vision in one eye; acuity is 20/200, there is an afferent defect, and the disc is pale and swollen with an altitudinal field defect. He mentions jaw pain when chewing. Reasoning: arteritic AION. Do not wait for serology - give IV steroids, check ESR/CRP and platelets, and arrange temporal artery biopsy. The fellow eye is at high risk within days.
Traps
Calling every swollen disc papilledema; missing giant cell arteritis in an elderly patient with visual loss; dismissing flashes as migraine; and not checking pupils before dilating.